Arduino Heart Rate Monitor

Project Description

Heart Rate Monitors are very popular at the moment.
There is something very appealing about watching the pattern of your own heart beat. And once you see it, there is an unstoppable urge to try and control it. This simple project will allow you to visualize your heart beat, and will calculate your heart rate. Keep reading to learn how to create your very own heart rate monitor.

 

Parts Required:

• Arduino UNO or compatible board
• Grove Base Shield
• Grove Ear-clip Heart Rate Sensor
• Grove Universal 4 pin cables
• LED and 330 ohm resistor

Fritzing Sketch

 

 
 
 

Grove Base Shield to Module Connections

 

 

Arduino Sketch

 

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/* =================================================================================================       Project: Arduino Heart rate monitor        Author: Scott C       Created: 21st April 2015   Arduino IDE: 1.6.2       Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html   Description: This is a simple sketch that uses a Grove Ear-clip Heart Rate sensor attached to an Arduino UNO,                which sends heart rate data to the computer via Serial communication. You can see the raw data                using the Serial monitor on the Arduino IDE, however, this sketch was specifically                designed to interface with the matching Processing sketch for a much nicer graphical display.                NO LIBRARIES REQUIRED. =================================================================================================== */ #define Heart 2                            //Attach the Grove Ear-clip sensor to digital pin 2. #define LED 4                              //Attach an LED to digital pin 4 boolean beat = false; /* This "beat" variable is used to control the timing of the Serial communication                                            so that data is only sent when there is a "change" in digital readings. */ //==SETUP========================================================================================== void setup() {   Serial.begin(9600); //Initialise serial communication   pinMode(Heart, INPUT); //Set digital pin 2 (heart rate sensor pin) as an INPUT   pinMode(LED, OUTPUT); //Set digital pin 4 (LED) to an OUTPUT } //==LOOP============================================================================================ void loop() {   if(digitalRead(Heart)>0){ //The heart rate sensor will trigger HIGH when there is a heart beat     if(!beat){ //Only send data when it first discovers a heart beat - otherwise it will send a high value multiple times       beat=true; //By changing the beat variable to true, it stops further transmissions of the high signal       digitalWrite(LED, HIGH); //Turn the LED on       Serial.println(1023); //Send the high value to the computer via Serial communication.     }   } else { //If the reading is LOW,     if(beat){ //and if this has just changed from HIGH to LOW (first low reading)       beat=false; //change the beat variable to false (to stop multiple transmissions)       digitalWrite(LED, LOW); //Turn the LED off.       Serial.println(0); //then send a low value to the computer via Serial communication.     }   } }

 
 
 
 

Processing Sketch

 

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/* =================================================================================================        Project: Arduino Heart rate monitor         Author: Scott C        Created: 21st April 2015 Processing IDE: 2.2.1        Website: http://arduinobasics.blogspot.com/p/arduino-basics-projects-page.html    Description: A Grove Ear-clip heart rate sensor allows an Arduino UNO to sense your pulse.                 The data obtained by the Arduino can then be sent to the computer via Serial communication                 which is then displayed graphically using this Processing sketch.                  =================================================================================================== */ import processing.serial.*; // Import the serial library to allow Serial communication with the Arduino int numOfRecs = 45; // numOfRecs: The number of rectangles to display across the screen Rectangle[] myRecs = new Rectangle[numOfRecs]; // myRecs[]: Is the array of Rectangles. Rectangle is a custom class (programmed within this sketch) Serial myPort;                                          String comPortString="0"; //comPortString: Is used to hold the string received from the Arduino float arduinoValue = 0; //arduinoValue: Is the float variable converted from comPortString boolean beat = false; // beat: Used to control for multiple high/low signals coming from the Arduino int totalTime = 0; // totalTime: Is the variable used to identify the total time between beats int lastTime = 0; // lastTime: Is the variable used to remember when the last beat took place int beatCounter = 0; // beatCounter: Is used to keep track of the number of beats (in order to calculate the average BPM) int totalBeats = 10; // totalBeats: Tells the computer that we want to calculate the average BPM using 10 beats. int[] BPM = new int[totalBeats]; // BPM[]: Is the Beat Per Minute (BPM) array - to hold 10 BPM calculations int sumBPM = 0; // sumBPM: Is used to sum the BPM[] array values, and is then used to calculate the average BPM. int avgBPM = 0; // avgBPM: Is the variable used to hold the average BPM calculated value. PFont f, f2; // f & f2 : Are font related variables. Used to store font properties. //==SETUP============================================================================================== void setup(){   size(displayWidth,displayHeight); // Set the size of the display to match the monitor width and height   smooth(); // Draw all shapes with smooth edges.   f = createFont("Arial",24); // Initialise the "f" font variable - used for the "calibrating" text displayed at the beginning   f2 = createFont("Arial",96); // Initialise the "f2" font variable - used for the avgBPM display on screen      for(int i=0; i<numOfRecs; i++){ // Initialise the array of rectangles     myRecs[i] = new Rectangle(i, numOfRecs);   }      for(int i=0; i<totalBeats; i++){ // Initialise the BPM array     BPM[i] = 0;   }      myPort = new Serial(this, Serial.list()[0], 9600); // Start Serial communication with the Arduino using a baud rate of 9600   myPort.bufferUntil('\n'); // Trigger a SerialEvent on new line } //==DRAW============================================================================================== void draw(){   background(0); // Set the background to BLACK (this clears the screen each time)   drawRecs();                                           // Method call to draw the rectangles on the screen   drawBPM();                                            // Method call to draw the avgBPM value to the top right of the screen } //==drawRecs========================================================================================== void drawRecs(){ // This custom method will draw the rectangles on the screen   myRecs[0].setSize(arduinoValue);                      // Set the first rectangle to match arduinoValue; any positive value will start the animation.   for(int i=numOfRecs-1; i>0; i--){ // The loop counts backwards for coding efficiency - and is used to draw all of the rectangles to screen     myRecs[i].setMult(i);                               // setMulti creates the specific curve pattern.     myRecs[i].setRed(avgBPM);                           // The rectangles become more "Red" with higher avgBPM values     myRecs[i].setSize(myRecs[i-1].getH());              // The current rectangle size is determined by the height of the rectangle immediately to it's left     fill(myRecs[i].getR(),myRecs[i].getG(), myRecs[i].getB()); // Set the colour of this rectangle     rect(myRecs[i].getX(), myRecs[i].getY(), myRecs[i].getW(), myRecs[i].getH()); // Draw this rectangle   } } //==drawBPM=========================================================================================== void drawBPM(){ // This custom method is used to calculate the avgBPM and draw it to screen.   sumBPM = 0;                                           // Reset the sumBPM variable   avgBPM = 0;                                           // Reset the avgBPM variable   boolean calibrating = false; // calibrating: this boolean variable is used to control when the avgBPM is displayed to screen      for(int i=1; i<totalBeats; i++){     sumBPM = sumBPM + BPM[i-1];                         // Sum all of the BPM values in the BPM array.     if(BPM[i-1]<1){ // If any BPM values are equal to 0, then set the calibrating variable to true.       calibrating = true; // This will be used later to display "calibrating" on the screen.     }   }   avgBPM = sumBPM/(totalBeats-1);                       // Calculate the average BPM from all BPM values                                                            fill(255); // The text will be displayed as WHITE text   if(calibrating){     textFont(f);     text("Calibrating", (4*width)/5, (height/5)); // If the calibrating variable is TRUE, then display the word "Calibrating" on screen     fill(0); // Change the fill and stroke to black (0) so that other text is "hidden" while calibrating variable is TRUE     stroke(0);   } else {     textFont(f2);     text(avgBPM, (4*width)/5, (height/5)); // If the calibrating variable is FALSE, then display the avgBPM variable on screen     stroke(255); // Change the stroke to white (255) to show the white line underlying the word BPM.   }       textFont(f);    text("BPM", (82*width)/100, (height/11)); // This will display the underlined word "BPM" when calibrating variable is FALSE.    line((80*width)/100, (height/10),(88*width)/100, (height/10));    stroke(0); } //==serialEvent=========================================================================================== void serialEvent(Serial cPort){ // This will be triggered every time a "new line" of data is received from the Arduino  comPortString = cPort.readStringUntil('\n'); // Read this data into the comPortString variable.  if(comPortString != null) { // If the comPortString variable is not NULL then    comPortString=trim(comPortString); // trim any white space around the text.    int i = int(map(Integer.parseInt(comPortString),1,1023,1,height)); // convert the string to an integer, and map the value so that the rectangle will fit within the screen.    arduinoValue = float(i); // Convert the integer into a float value.    if (!beat){      if(arduinoValue>0){ // When a beat is detected, the "trigger" method is called.        trigger(millis()); // millis() creates a timeStamp of when the beat occured.        beat=true; // The beat variable is changed to TRUE to register that a beat has been detected.      }    }    if (arduinoValue<1){ // When the Arduino value returns back to zero, we will need to change the beat status to FALSE.      beat = false;    }  } }  //==trigger=========================================================================================== void trigger(int time){ // This method is used to calculate the Beats per Minute (BPM) and to store the last 10 BPMs into the BPM[] array.   totalTime = time - lastTime;                         // totalTime = the current beat time minus the last time there was a beat.   lastTime = time;                                     // Set the lastTime variable to the current "time" for the next round of calculations.   BPM[beatCounter] = 60000/totalTime;                  // Calculate BPM from the totalTime. 60000 = 1 minute.   beatCounter++;                                       // Increment the beatCounter   if (beatCounter>totalBeats-1){ // Reset the beatCounter when the total number of BPMs have been stored into the BPM[] array.     beatCounter=0;                                     // This allows us to keep the last 10 BPM calculations at all times.   } } //==sketchFullScreen========================================================================================== boolean sketchFullScreen() { // This puts Processing into Full Screen Mode  return true; } //==Rectangle CLASS==================================================================================********* class Rectangle{   float xPos, defaultY, yPos, myWidth, myHeight, myMultiplier; // Variables used for drawing rectangles   int blueVal, greenVal, redVal; // Variables used for the rectangle colour      Rectangle(int recNum, int nRecs){ // The rectangles are constructed using two variables. The total number of rectangles to be displayed, and the identification of this rectangle (recNum)     myWidth = displayWidth/nRecs; // The width of the rectangle is determined by the screen width and the total number of rectangles.     xPos = recNum * myWidth;                                      // The x Position of this rectangle is determined by the width of the rectangles (all same) and the rectangle identifier.     defaultY=displayHeight/2; // The default Y position of the rectangle is half way down the screen.     yPos = defaultY;                                              // yPos is used to adjust the position of the rectangle as the size changes.     myHeight = 1;                                                 // The height of the rectangle starts at 1 pixel     myMultiplier = 1;                                             // The myMultiplier variable will be used to create the funnel shaped path for the rectangles.     redVal = 0;                                                   // The red Value starts off being 0 - but changes with avgBPM. Higher avgBPM means higher redVal          if (recNum>0){ // The blue Value progressively increases with every rectangle (moving to the right of the screen)       blueVal = (recNum*255)/nRecs;     } else {       blueVal = 0;     }     greenVal = 255-blueVal;                                       // Initially, the green value is at the opposite end of the spectrum to the blue value.   }      void setSize(float newSize){ // This is used to set the new size of each rectangle     myHeight=newSize*myMultiplier;     yPos=defaultY-(newSize/2);   }      void setMult(int i){ // The multiplier is a function of COS, which means that it varies from 1 to 0.     myMultiplier = cos(radians(i)); // You can try other functions to experience different effects.   }      void setRed(int r){     redVal = int(constrain(map(float(r), 60, 100, 0, 255),0,255)); // setRed is used to change the redValue based on the "normal" value for resting BPM (60-100).     greenVal = 255 - redVal;                                       // When the avgBPM > 100, redVal will equal 255, and the greenVal will equal 0.   }                                                                // When the avgBPM < 60, redVal will equal 0, and greenVal will equal 255.      float getX(){ // get the x Position of the rectangle     return xPos;   }     float getY(){ // get the y Position of the rectangle     return yPos;   }      float getW(){ // get the width of the rectangle     return myWidth;   }      float getH(){ // get the height of the rectangle     return myHeight;   }      float getM(){ // get the Multiplier of the rectangle     return myMultiplier;   }      int getB(){ // get the "blue" component of the rectangle colour     return blueVal;   }      int getR(){ // get the "red" component of the rectangle colour     return redVal;   }      int getG(){ // get the "green" component of the rectangle colour     return greenVal;   } }

 

Processing Code Discussion:

The Rectangle class was created to store relevant information about each rectangle. By using a custom class, we were able to design our rectangles any way we wanted. These rectangles have properties and methods which allow us to easily control their position, size and colour. By adding some smart functionality to each rectangle, we were able to get the rectangle to automatically position and colour itself based on key values.

The Serial library is used to allow communication with the Arduino. In this Processing sketch, the values obtained from the Arduino were converted to floats to allow easy calulations of the beats per minute (BPM). I am aware that I have over-engineered the serialEvent method somewhat, because the Arduino is only really sending two values. I didn't really need to convert the String. But I am happy with the end result, and it does the job I needed it to...

This project is quite simple. I designed it so that you could omit the Processing code if you wanted to. In that scenario, you would only be left with a blinking LED that blinks in time with your pulse. The Processing code takes this project to the next level. It provides a nice animation and calculates the beats per minute (BPM).
 
I hope you liked this tutorial. Please feel free to share it, comment or give it a plus one. If you didn't like it, I would still appreciate your constructive feedback.

 

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